Cryogenic transfer line arrangement



July 25, 1967 D. B. MANN CRYOGENIC TRANSFER LI NE ARRANGEMENT Filed May 15, 1.964

FIG

N Wm WM m5 E m\ G U 0 D WEB/Y ATTORNEYS United States Patent 3,332,446 CRYOGENIC TRANSFER LHNE ARRANGEMENT Douglas B. Mann, 3110 23rd St, Boulder, Colo. 80302 Filed May 15, 1964, Ser. No. 367,815 6 Claims. (Cl. 138114) My invention rel-ates to a cryogenic transfer line arrangement, and more particularly, to conduiting especially adapted to serve as a transfer line for super cold or cryogenic liquids such as liquid hydrogen, helium, or nitrogen. 7

Conventional cryogenic high quality transfer lines (for liquid hydrogen, nitrogen, etc.) are essentially hand-fabricated items requiring considerable painstaking skill to make, and close control of assembly procedures is also required because of the high cleanliness requirements. While line sizes vary from less than one inch to over eighteen inches in diameter, the method of construction has not changed materially in twenty-five years, and consists primarily of the same constructional principles involved in constructing a vacuum insulated vessel. Close control of assembly procedures is required as even fingerprints will materially affect the performance of the line.

Lines of this type consist of rigid piping of a suitable material that is thoroughly cleaned and frequently specially treated with acid to improve surface qualities and eliminate out-gasing. After suitable spacers are slipped over the piping, an outer vacuum jacket, after having been thoroughly cleaned and treated in a similar manner, is slipped over the spacers and the pipe. Thereafter the ends of the resulting conduiting are closed and the vacuum space between the pipe and the jacket is pumped down to a hard vacuum (10" mm. of Hg or less).

As these lines cannot be readily fabricated in the field because of the high cleanliness requirement, they must be made up in shops in appropriate lengths and shipped to the point of use. Since these lines comprise rigid tubing, they have to be limited in length to the longest practical shipping length, which is 40 feet (for railroad car shipments). The individual 40 foot sections are assembled in the field using known techniques, which ordinarily involves suspending the pipe lengths between pedestal type mountings and welding the joints between the lengths one at a time, which again involves a considerable amount of hand Work even in the assembly process.

Furthermore, considerable relative movement occurs between the inner and outer conduit members of these lines axially of the line, and some sort of bellows type expansion arrangement must be incorporated in either the inner or outer conduit, preferably the inner conduit.

Consequently, such lines are quite expensive, a one-inch line running on the order of thirty-five dollars a foot plus the cost of connectors at each end.

Cryogenic lines for low quality application (for liquid oxygen, nitrogen, methane, and the like) conventionally comprise ordinary piping put up by pipefitters and then lagged with bulk insulation that must be sealed to prevent moisture condensation and freezing, as by using vapor barrier type tape or some sort of asphaltic compound. Consequently, a lot of hard work goes into fabrication of even lines of this type, making even low quality installations excessively costly.

A principal object of my invention is to provide a low-. cost semi-flexible, cryogenic transfer line structural arrangement that may be inexpensively and readily manufactured and packaged for shipping in thousand foot or multiples thereof lengths by coiling same on large diameter reels.

Another principal object of the invention is to provide a cryogenic transfer line arrangement that permits a striking increase in the amount of transfer line footage 3,332,446 Patented July 25, 1967 ice that may be shipped as a package, and yet permit the package to be shipped either by rail or by truck Without requiring occupation of the entire vehicle.

Still another object of the invention is to provide a cryogenic transfer line arrangement which provides cryogenic conduiting that may be supplied to the user in long lengths that may be cut to fit any particular installation and installed without any particular pains being taken to support or brace it.

Other objects of the invention are to provide a cryogenic transfer line that is readily adapted for both high and low quality transfer line applications, to provide methods of assembly of cryogenic transfer lines that eliminate most of the hand fabrication now required, both in manufacture of the line and in its assembly at the job site, and to provide cryogenic transfer line arrangements that are convenient to install, that require only minimum maintenance, and that are suitable for use in a wide variety of cryogenic operations.

Other objects, uses and advantages will be obvious or become apparent from a consideration of the following detailed description and the application drawings.

In the drawings:

FIGURE 1 is a diagrammatic cross-sectional view along the axis of a cryogenic transfer line embodying the preferred form of the invention;

FIGURE 2 is a view similar to that of FIGURE 1 illustrating a modified form of the invention; and

FIGURE 3 is a diagrammatic fragmental view illustrating a feature of the spacer member that may be used in the embodiments of FIGURES 1 and 2.

However, it is to be understood that the drawing illustrations provided are supplied primarily for the purpose of complying with 35 U.S.C. 112, and that the invention may have other specific embodiments.

Reference numeral 10 of FIGURE 1 indicates a preferred embodiment of the invention which comprises a semi-fiexible cryogenic transfer line including a semiflexible inner tubing or conduit 12 formed from a material having a high surface reflectivity, such as copper, a spirally wound, flexible spacer member 14 in the form of a strip of heat insulating material such as polyethylene, a semi-flexible outer conduit or tubing 16 of a material similar to that of tubing 12 and received over the spacer member 14 and inner conduit 12 in substantial concentric relation through the latter, and an outer covering or coating 18 of a suitable flexible wear resisting substance such as neoprene or some suitable synthetic plastic material such as polyethylene.

The transfer line 10 is preferably made by taking a flat sheet of tubing, formed from the material to be employed, such as copper, aluminum, or stainless steel (depending on the application), which sheet should be quadrilaterally contoured in configuration and having a length according to the length of tubing to be produced, and pulling the sheet through a suitable form which bends it into a cylindrical configuration that disposes the two longitudinally extending edges thereof in substantial abutting relation.

After the tube issues from the forming die, it is butt welded along the seam defined by the two abutting edges.

The resulting tube is then passed through a conventional shaping or convolution chasing machine which chases spirally shaped convolutions or indentations 20 into the tube and gives it the spiralling indentation appearance indicated in FIGURE 1. The convolutions 20 preferably have a lead that is on the order of one-half inch (that is, each convolution makes a 360 degree turn in one-half inch of length of the tube or conduit 12). The lead should not greatly exceed this as the flexibility of the line would be affected.

A convolution chasing machine that effects this shaping comprises hardened polished steel wheels set for rotation about axes that form skew angles with respect to the axis of the tube at the desired lead. These wheels have transverse cross-sectional configurations (in the plane of their respective axes) that lie on an arc of a circle and the wheels are pressed against the tube as the tube moves lengthwise of itself through the shaping machine to provide the spiralling indentations indicated.

.14 face generally longitudinally of the conduit.

The outer edge 26 of the member 14 is preferably notched as at 28 (see FIGURE 3) so that when the member 14 is spirally wound in the manner indicated, it defines outwardly extending projections 30 that extend radially outwardly of the inner tube or conduit 12. These projections are shown in FIGURE 3, and reduce the area of contact between spacer member 14 and outer conduit 16. In the specific showings of FIGURES 1 and 2, the notches 28 are omitted.

The subassembly consisting of the inner tube or conduit 12 and the spirally wound spacer member 14 is then placed in operative relation to a second forming die in cooperative relation with a second quadrilaterally shaped flat sheet that is to form the outer conduit or tube 16. The second sheet is shaped from its flat configuration to a cylindrical configuration with its longitudinally extending edges in abutting relation, in a manner similar to that described in connection with the conduit 12, and preferably this is done by simultaneously drawing the second sheet and the subassembly through the die. As the outer tube 16 and the subassembly it surrounds emerge from the form that is involved, the longitudinally extending edges of the sheet that forms tube 16 are butt welded together, after which the transfer line unit passes through a shaping or chasing machine that chases on the outer tube 16 spiralled indentations or convolutions 32 that are identical to convolutions 20 of conduit 12. Preferably, the chasing is done in connection with the tube 16 in such a manner that the convolutions are forced into intimate contact with the spacer member 14 thereby securely binding the tubular member 12, the spacer member 14 and the outer tubular member 16 together.

The spiralled indentations 20 and 32, which have substantially the same lead, plus the relative thinness of the tubular wall structures defining conduiting 12 and 14, make the transfer line sufficiently flexible for coiling on reels (and for shaping as desired when applied to cryogenic apparatus); however, the indentations provide reinforcement against buckling and atmospheric and other pressures that the line 10 will be subjected to in service.

Finally, the outer protective coating 18 is applied to the outer surface 49 of the outer tubular member 16, and the coating 18, which is merely diagrammatically illustrated, may comprise an extruded layer of neoprene or some similar natural or synthetic rubber or plastic material, in which case the conduit unit consisting of the joined members 12, 14 and 16 is drawn through an extruding mechanism that applies the coating 18.

Alternately, the coating 18 may consist of strips of plastic material wrapped in a spiral manner about the outer surface 36 of the conduit 16.

Where the coating 18 comprises a rubber or rubber-like material, it should be vulcanized as a final step and this may be done by drawing the tubing through a continuous vulcanizing machine.

The embodiment of FIGURE 1 thus permits the setting up of a substantially continuous process for making cryogenie transfer lines in which the lines issue substantially continuously from the apparatus involved for coiling on reels for storage and shipping.

FIGURE 2 illustrates an alternate embodiment 48 of the invention involving an inner seamless tube or conduit 50, a spacer member 14A that is identical to the spacer member 14, an outer seamless tube or conduit 52 which has applied thereto the coating 18 that has been previously described.

The conduit 48 of FIGURE 2 is made by soft drawing tube 50 from a material such as copper, aluminum or stainless steel (depending upon the application), in the length desired but preferably continuously and then spirally winding spacer member 14A about the outer surface 54 of tubular member 50 (with the lead aforedescr-ibed), after which the subassembly consisting of the tube or tubular member 50 and the spacer member 14A is drawn into or has continuously formed thereabout tube 52, formed from a material similar to that specified for the tube 50. Both tubes are simultaneously pulled through a swedging machine that swedges the outer member into binding engagement with the spacer member 14A, after which the coating 18 is applied in the manner similar to that already described.

Thus, the embodiment of FIGURE 2 may be continuously made to supply line 48 in endless lengths that may be cut to desired lengths. Alternately, the tubing 50 and 52 may be made up in lengths of 1,000 feet or a multiple thereof, and after the spacer member 14 is applied to the inner tube, the resulting subassembly is then pulled into the outer tube which is then swedged in the manner already indicated.

The thickness of the wall structure making up conduits 50 and 52 should be thin enough to render line 48 semi-flexible in the sense that it can be coiled on a reel.

In connection with the embodiment of FIGURE 1, the depth of the convolutions 20 and 32 should lie in the range from about to about A; of an inch radially of the conduit 10. This avoids having the convolutions define black body type radiation traps.

In both embodiments of the invention, the inner and outer surfaces of the inner and outer conduits should be kept substantially grease-free and uncoated for high reflectivity characteristics. 7

It is intended that both embodiments of the invention be manufactured either continuously or in thousand foot lengths or multiples thereof, and it will be found that they are both sufiiciently flexible to permit them to be wound on nine foot diameter reels.

In the embodiment of FIGURE 1, the convolutions have been found to make the transfer line 10 not only semi-flexible transversely thereof, but also semi-flexible axially thereof in that the conduits may flex longitudinally thereof, that is, expand or contract, thereby avoiding the need for line differential contraction joints.

In the embodiment of FIGURE 2, an expansion joint of any conventional type should be applied to either the inner or the outer tube at every 40 feet of length to insure the desired longitudinal flexibility.

In use, the conduits 10 or 48 may be packaged on nine foot reels in thousand foot lengths or multiples thereof, and shipped in this condition to the point of use. The reel packaging of the conduiting means that a substantial footage of transfer line can be confinexl to a single package and transported on a railroad car without using the entire railroad car. Heretofore, rigid type'cryogenic transfer lines have required an entire railroad car whether a single conduit or a hundred conduit lengths were to be carried.

Furthermore, the reel type packaging permits truck transit of the transfer line conduiting for the first time.

When the conduiting is taken to the place of installation, it may be utilized by merely unwinding it, cutting it to fit between apparatus to be connected cryogenically,

connecting conventional cryogenic connectors to the conducting ends, connecting the conventional connectors to the apparatus that is involved at either end of the transfer line, and then evacuating the vacuum space between the inner and outer conduits to a vacuum on the order of 1 mm. of Hg absolute. No special care need be taken to provide supports for the conduiting and it may be draped Where convenient over the distance between the intake and discharge end of the transmission line.

Furthermore, the transmission lines and 48 may be buried underground where installations of this type are conduited, all without requiring any special reinforcement or-protection.

In a successful embodiment of line 10, the tube 12 has an CD. of 1.150 inches, an ID. of .950 inch and a .025 inch wall thickness, the spacer member 14 has a transverse section of .725 by .250 and notches 28 are .125 inch lengthwise of the spacer and. inch deep and spaced inch apart; conduit 16 has an CD. of 2.850 inches, an ID. of 2.500 inches and an .025 Wall thickness, and coating 18 has an CD. of 3.000 inches, an ID. of 2.850 inches and a thickness of .075 inch.

In a successful embodiment of line 48, conduit 50 has an CD. of 1.155 inches, an ID. of 1.01 inches, and a wall thickness of .072 inch, spacer member 14A is the equivalent of member 14, conduit 52 has an OD. of 3.125 inches, an ID. of 2.855 inches, and a .135 inch wall thickness, and coating 18 has an CD. of 3.250 inches, an ID. of 3.125 inches, and a .063 inch wall thickness.

It will therefore be seen that I have provided for the first time a practical arrangement in a semi-flexible cryogenic transfer line which permits the transfer line to be constructed in continuous lengths of from one thousand to four thousand feet or any desired length, as compared to the forty feet maximum length now conventionally encountered.

Furthermore, the cost per foot of conduiting of this type is from fifteen to twenty percent of the cost of conventional. cryogenic transfer lines. One reason for the great reduction in cost is the mass production techniques described above that may be employed in the manufacture of the transfer lines.

The embodiment of FIGURE 1 is particularly advantageous as it. requires no expansion joints from end-to end as the convolutions 20 and 32 provide the longitudinal and sidewise semi-flexibility desired while at the same time insuring adequate stiffness and strength for the purpose desired. 1

The protective outer coatings 18 permit the transfer lines to be used in areas of corrosive atmosphere, such as near the ocean, or underground, with equal facility.

The foregoing description and the drawings are given merely to explain and illustrate my invention and the invention is not to be limited thereto, except insofar as the appended claims are so limited, since those skilled in the art who have my disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.

The Government of the United States of America shall have a non-exclusive, irrevocable, royalty-free license to practice this invention with power to grant licenses for all governmental purposes.

I claim.

1. A semi-flexible cryogenic transfer line adapted to be made in long continuous lengths and supplied in coiled form, said line comprising:

laterally and longitudinally flexible cryogenic transfer line means for conducting cryogenic fluids and characterized by being coilable in long lengths and cut to fit specific applications,

said transfer line means comprising:

a semi-flexible inner tube formed from a material having high surface reflectivity,

a heat insulating spacer member received over said inner tube in spirally wound relation therealong and having a lead in the range of from about six to about ten inches,

said spacer member being of quadrilateral trans- V verse configuration,

a semi-flexible outer tube formed from a material having high surface reflectivity and received in concentric relation over said inner tube and said spacer,

said inner and outer tubes being in binding engagement with said spacer member along the length thereof whereby thermal contraction of said inner tube under the presence of cryogenic substances contained therein is transmitted to said outer tube,

and a protective flexible coating covering the outer surface of said outer tube,

with the inner and outer surfaces of said inner tube and the inner surface of said outer tube being substantially grease free and uncoated for maximum reflectivity characteristics,

and said surfaces and the outer surface of said outer tube being free of black body type radiation traps.

2. The cryogenic transfer line set forth in claim 1 wherein:

said tubes are formed from seamless tubing, said outer tube being in swedged relation against said spacer member and said inner tube to provide said binding relation.

3. The cryogenic transfer line set forth in claim 1 wherein:

said spacer member has its radially outward edge formed with spaced outwardly opening notches.

4. A semi-flexible cryogenic transfer line adapted to be made in long continuous lengths and supplied in coiled form, said line comprising:

laterally and longitudinally flexible cryogenic transfer line means for conducting cryogenic fluids and characterized by being coilable in long lengths and cut to fit specific applications,

said transfer line means comprising:

a. semi-flexible inner tube defined by sheeting material formed from a material having high surface reflectivity and formed to define a tubular wall structure,

said wall structure having spirally shaped convolutions formed therein and extending longitudinally thereof and having a lead on the order of about one-half inch,

heat insulating spacer means received over said inner tube and extending longitudinally thereof,

said spacer means comprises an elongated spacer member formed from heat insulating material and spirally wound about said inner tube 51 d having a lead that is in the range of from about six inches to about ten inches,

said spacer member being of quadrilateral transverse cross-sectional configuration,

a semi-flexible outer tube defined by sheeting material formed from a material having high surface reflectivity and formed to define a tubular wall structure received over said inner tube and said spacer means,

said outer tube wall structure having spirally shaped convolutions formed therein and extending longitudinally thereof and having a lead on the order of about one-half inch,

said inner and outer tube wall structures being in binding engagement with said spacer member along the length thereof whereby thermal contraction of said inner tube under the temperatures of cryogenic substances contained therein is transmitted to said outer tube,

F i said convolutions of said tubes having a depth which does not exceed about /a of an inch, and a flexible wear resistant coating covering the outer surface of said outer tube, with the inner and outer surfaces of said inner tube and the inner surface of said outer tube being substantially grease free and uncoated for maximum reflectivity characteristics. 5. The cryogenic transfer line set forth in claim 4 wherein:

said spacer member has the outer edge thereof formed with spaced outwardly opening notches.

6. The cryogenic transfer line set forth in claim 4 wherein:

8 References Cited UNITED STATES PATENTS 644,841 3/1900 Allen Q 138148 X 675,447 6/1901 McMahon 138-148 2,409,304 10/1946 Morrison 138'122 X 2,664,112 12/1953 Isenberg 138113 2,756,032 7/1956 Dowell 138-148 X FOREIGN PATENTS 784,698 10/1957 Great Britain.

LAVERNE D. GEIGER, Primary Examiner.

SAMUEL ROTHBERG, Examiner.

said line is formed in a long length and coiled for 15 C. L. HOUCK, Assistant Examiner.

handling in bulk form. 

1. A SEMI-FLEXIBLE CYROGENIC TRANSFER LINE ADAPTED TO BE MADE IN LONG CONTINUOUS LENGTHS AND SUPPLIED IN COILED FORM, SAID LINE COMPRISING: LATERALLY AND LONGITUDINALLY FLEXIBLE CRYOGENIC TRANSFER LINE MEANS FOR CONDUCTING CRYOGENIC FLUIDS AND CHARACTERIZED BY BEING COILABLE IN LONG LENGTHS AND CUT TO FIT SPECIFIC APPLICATIONS, SAID TRANSFER LINE MEANS COMPRISING: A SEMI-FLEXIBLE INNER TUBE FORMED FROM A MATERIAL HAVING HIGH SURFACE REFLECTIVITY, A HEAT INSULATING SPACER MEMBER RECEIVED OVER SAID INNER TUBE IN SPIRALLY WOUND RELATION THEREALONG AND HAVING A LEAD IN THE RANGE OF FROM ABOUT SIX TO ABOUT TEN INCHES, SAID SPACER MEMBER BEING OF QUADRILATERAL TRANSVERSE CONFIGURATION, A SEMI-FLEXIBLE OUTER TUBE FORMED FROM A MATERIAL HAVING HIGH SURFACE REFLECTIVITY AND RECEIVED IN CONCENTRIC RELATION OVER SAID INNER TUBE AND SAID SPACER, SAID INNER AND OUTER TUBES BEING IN BINDING ENGAGEMENT WITH SAID SPACER MEMBER ALONG THE LENGTH THEREOF WHEREBY THERMAL CONTRACTION OF SAID INNER TUBE UNDER THE PRESENCE OF CRYOGENIC SUBSTANCES CONTAINED THEREIN IS TRANSMITTED TO SAID OUTER TUBE, AND A PROTECTIVE FLEXIBLE COATING COVERING THE OUTER SURFACE OF SAID OUTER TUBE, WITH THE INNER AND OUTER SURFACES OF SAID INNER TUBE AND THE INNER SURFACE OF SAID OUTER TUBE BEING SUBSTANTIALLY GREASE FREE AND UNCOATED FOR MAXIMUM REFLECTIVITY CHARACTERISTICS, AND SAID SURFACES AND THE OUTER SURFACE OF SAID OUTER TUBE BEING FREE OF BLACK BODY TYPE RADIATION TRAPS. 